Improve the following sentence by choosing the most appropriate connector: This scooter is not as efficient as it used to be; _____ it is still a very useful machine.

Introduction / Context:
This sentence improvement question tests your understanding of logical connectors and contrast in English. The sentence compares the present condition of a scooter with its past efficiency but then adds that it is still very useful. The blank needs a connector that clearly expresses contrast between reduced efficiency and continued usefulness, without changing the basic meaning of the statement.

Given Data / Assumptions:
- Original sentence: This scooter is not as efficient as it used to be; _____ it is still a very useful machine.
- The first clause is negative in tone and tells us that efficiency has decreased.
- The second clause adds a positive point that it remains useful.
- Options: similarly, further more, nevertheless, No improvement, instead.

Concept / Approach:
We need a connector that signals contrast between two ideas: one negative and one positive. Words like nevertheless and however are typical contrast markers, showing that the second statement is surprising in light of the first. Similarly is used to show similarity, not contrast. Furthermore or further more introduces an additional point in the same direction, not an opposite idea. Instead suggests replacement, as in one thing happening rather than another. Therefore, the only connector that correctly signals contrast while preserving the meaning is nevertheless.

Step-by-Step Solution:
Step 1: Identify the relationship between the two clauses. The first talks about reduced efficiency, the second about continued usefulness.
Step 2: Recognise that a contrast marker is required, because the second clause softens or balances the first.
Step 3: Among the options, select the word that expresses contrast without implying replacement or addition in the same direction.
Step 4: Insert nevertheless and read the complete sentence: This scooter is not as efficient as it used to be; nevertheless it is still a very useful machine.

Verification / Alternative check:
Reading the sentence with nevertheless clearly conveys the intended sense: despite the decline in efficiency, the scooter remains useful. Try replacing it with similarly or further more and the sentence becomes illogical, because these words suggest an additional negative detail or a similar statement rather than a balancing positive point. Using instead would mean that the scooter is not efficient but is useful in place of that, which does not capture the nuance that it is simultaneously less efficient and still useful.

Why Other Options Are Wrong:
- similarly: suggests that what follows is similar in nature to what comes before, but here we want a contrast between less efficient and still useful.
- further more: means in addition and is used to add another reason or point, usually reinforcing the same idea, not balancing it.
- No improvement: is incorrect because the sentence without a connector sounds abrupt and incomplete; it needs a linking word for clarity.
- instead: implies replacement, which would suggest that usefulness exists in place of efficiency, rather than alongside it in a contrasting way.

Common Pitfalls:
Many learners misread such questions and focus only on the second clause, ignoring how it relates to the first. Always pay attention to whether the second clause supports, contrasts with, or replaces the information in the first. Matching the connector to this relationship is the key to choosing correctly. In exam practice, learn to recognise common contrast markers like however, nevertheless, yet, and still, and practise using them in sentences.

Final Answer:
The best improvement is to use nevertheless, giving: This scooter is not as efficient as it used to be; nevertheless it is still a very useful machine.